PracticalDermatology

Basosquamous carcinoma (BSC) is a form of poorly differentiated squamous cell carcinoma that has a histological similarity to basal cell carcinoma.^1-10 BSC currently represents approximately 2% of all non-melanoma skin malignancies. The majority of cases are found in the head and neck region with predilection for older Caucasian males.¹⁰ Herein we report four cases of basosquamous carcinoma.

This is a retrospective clinical review of four patients with basosquamous carcinoma. Three patients were seen by otolaryngologists at Ochsner-LSU Health Shreveport, and one patient was seen by the dermatology service at Ochsner-LSU St. Mary’s Medical Center. Three patients were female, and one was male, with an average age of 65 years. In all cases, the diagnosis of basosquamous carcinoma was made by biopsy and histologic examination. Two of the patients had a known history of basosquamous carcinoma, with recurrence of disease after initial removal. One patient had a history of previous squamous cell carcinoma. We performed this study with the intention of examining the presentation and analyzing the clinical characteristics of each case.

Case 1

A 61-year-old man presented with a lesion on his left hand that had been present for 1 year and was initially believed by the patient to be a wart. The lesion became more painful and enlarged. He tried to self-treat with peroxide and manipulating the lesion to make it fall off without any improvement. He denies bleeding of the lesion. He stated he previously worked as a roofer for many years and denies sunscreen use. The patient had past medical history of squamous cell carcinoma in situ of the forehead, multiple actinic keratosis on the bilateral arms and scalp, hemorrhoids, hypertension, and tobacco dependence. There was no known family history of skin cancer. Physical exam revealed a hyperkeratotic and necrotic plaque with underlying friable tissue on the left dorsal hand (Fig 1). Shave biopsy revealed basaloid carcinoma with clear cell change, involving the biopsy border. This neoplasm demonstrates an unusual phenotype with the positive keratin 20 stain and possible focal weak CDX2 positive stain.

Fig 1. Hyperkeratotic and necrotic plaque with underlying friable tissue.

Case 2

A 77-year-old female presented for evaluation of a lesion on the left superior auricle. The patient has a significant past medical history of cardiac stent placement (on clopidogrel and rivaroxaban), type 2 diabetes mellitus, status-post left lower leg amputation, significant renal disease, and 25 pack-per-year smoking history. Physical exam revealed a previous biopsy site of the left ear. New biopsy excision revealed invasive basosquamous carcinoma, metatypical type.

Case 3

A 59-year-old female presented with a right nasal lesion that had been present for the past 5 years. She had previously had the lesion removed, but it progressively continued to grow after removal. Patient stated the lesion started to become ulcerated and drain. She has a past medical history of Gitelman syndrome, left total knee replacement, and former smoking history. Physical exam revealed an ulcerative lesion of the right nasal wall (Fig 2). Biopsy revealed basosquamous carcinoma of the right nose (Fig 3, 4), requiring partial rhinectomy for complete surgical removal.

Fig 2. Ulcerative lesion of the right nasal wall.

Fig 3. Basal cell carcinoma area composed of basaloid tumor cells with peripheral palisading and myxoid stromal change (hematoxylin-eosin, original magnification x 10).

Fig 4. Squamous cell carcinoma area composed of tumor cells with eosinophilic cytoplasm and evidence of keratinization and keratin pearls (hematoxylin-eosin, original magnification x 10).

Case 4

A 62-year-old female with a past medical history of chronic obstructive pulmonary disease presented to the emergency department with an ulcerative lesion on her nose. The patient reported she had this lesion for many years, but that it grew in size over the last few months prior to presentation. The patient reported the lesion is tender. She endorsed a 47-pack-per-year smoking history. Physical exam showed a complete erosion of the left nasal sidewall involving the mucosa and skin, with absence of left nasal ala. Biopsy revealed basosquamous carcinoma, requiring partial rhinectomy for complete resection.

DISCUSSION

Basaloid carcinoma is a form of poorly-differentiated squamous cell carcinoma that shares histologic similarities with basal cell carcinoma.¹⁰ Clear cell change is an uncommon variant of basal cell neoplasms, characterized by areas of glycogen, lipid, and degenerative change, resulting in a portion of or the entire tumor containing cells with clear cytoplasm.^1,4 As seen in Case 1, this unique presentation affected the dorsal hand, whereas our other cases affected the head and neck region. The differential diagnosis for this histopathologic pattern includes a pleomorphic nodular basal cell carcinoma with aberrant interstitial phenotypic differentiation, squamous cell carcinoma with clear cell change and interstitial phenotypic differentiation, and trichoblastic carcinoma with aberrant interstitial phenotypic differentiation. The positive keratin 20 and possible focal CDX2 positive staining raises the remote possibility of an unusual metastatic lesion from the lower gatrointerstitial tract.

A basosquamous carcinoma (BSC) contains histological components of both basaloid and squamous differentiation. It is often referred to as a collision between a basal cell tumor and a separate squamous cell tumor, resulting in one highly invasive carcinoma with a high likelihood of recurrence and metastasis.^2,5,6 Two of our patients had previously undergone complete surgical excision of similar lesions in the same areas, demonstrating this frequent feature of recurrence. Two of our patients also reported noticing their lesion for multiple years, which is a common characteristic of basosquamous carcinoma.⁹ BSC is most commonly found in the head and neck region, and of our four patients with biopsy-proven BSC, two of the lesions were localized to the nose, and one to the ear.^2,5,6,9

The diagnosis of BSC can only be made after biopsy and histological investigation of the suspected lesion.^5,9 The clinical appearance of basosquamous carcinoma is frequently indistinguishable from basal cell carcinoma due to their similar appearances and presenting locations.⁵ Though there is some uncertainty in the literature surrounding the definition of BSC, and the common histological finding in order to make a diagnosis is noted areas of both squamous cell and basal cell carcinoma without clear separation.^5,9

These lesions should be treated similarly to aggressive variants of basal cell carcinomas.⁵ Treatment options include excision, Mohs micrographic surgery, surgery with radiation, cryotherapy, chemotherapy, SMO antagonists, and others. There is no determined standard of care for BSC due to a lack of consistency with treatments and outcomes.⁹

The authors have received no funding for this manuscript. They report no conflicts of interest.

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